1. Field of the Invention
The present invention relates to a honeycomb structured body.
2. Discussion of the Background
In recent years, particulates, such as soot, contained in exhaust gases discharged from internal combustion engines of vehicles such as buses and trucks, and construction machines, have raised serious problems, as those particulates are harmful to the environment and the human body.
For this reason, there have been proposed various filters using a honeycomb structured body as a ceramic filters which are porous ceramics made of cordierite, SiC and the like and made to pass through exhaust gases to capture particulates in exhaust gases so as to purify the exhaust gases, have been proposed.
Normally, in such a ceramic filter, a cell wall, that separates a plurality of cells placed in parallel in the same direction and forming a pillar-shaped body, from one another, is allowed to function as a filter.
Namely, in the above-mentioned honeycomb filter, either of the exhaust gas-inlet side or the exhaust gas-outlet side of the end portions of the cells, which are formed into the above-mentioned pillar-shaped body, is sealed with a plug in so-called a checkered pattern. Thus, exhaust gases that flow into one cell are allowed to always pass through the cell wall which separates the cells from one another and flow out from another cell, and when exhaust gases pass through these cell walls, particulates are captured at the cell wall portion to purify exhaust gases.
As this exhaust gas purifying function is exerted, particulates gradually deposit on the portion of cell walls which separate cells of the honeycomb filter, and clogging occurs to block ventilation. Therefore, the honeycomb filter needs to be periodically subjected to a regenerating process, in which particulates that cause clogging are burned to be removed, in order to regenerate the honeycomb filter.
Accordingly, the honeycomb filter is required, as its characteristics in addition to high capture efficiency and low pressure loss, to be free from occurrence of cracks or erosion in the regenerating processes, and further, to be free from heat deterioration of a catalyst, if a catalyst is supported thereon.
With respect to a honeycomb filter which is low in pressure loss and free from occurrence of cracks and erosion loss in regenerating processes, there is proposed a ceramic filter having a honeycomb bulk density of at least about 0.50 g/cm3 and an effective aspect ratio of the length to the diameter of not more than about 0.9, and provided with a porous ceramic honeycomb structured body with closed end portions for capturing and burning diesel exhaust fine particles (JP-A 2003-515023).
Further, in JP-A 2003-515023, it is described that the porosity of the cell wall is normally about 50%, and when the porosity exceeds 70%, the integrity as a ceramic filter is questionable.
The contents of JP-A 2003-515023 are incorporated herein by reference in their entirety.